Hi, I’m currently attempting to replace the PCV valve on my Mk3 NC as I believe the current one has failed. The car uses large amounts of oil and is smoking at high revs. After researching many sites, the problem could be caused either sticking oil control rings, faulty PCV valve or simply worn bores, although the cylinders all have good compression and are within 5psi of each other.
As you may know, unlike the earlier models that have the PCV valve within easy access on the cam cover, the PCV on the NC is located on the inlet side of engine, under the inlet manifold assembly. The only way to access the PCV is to remove the inlet manifold, which is easier said than done.
I’ve been using the Mellen’s workshop manual to try and release the inlet manifold assembly, but have come to a problem that appears impossible to solve. With all of the accessories and fixing bolts removed, the inlet manifold is still tied to the engine by the EGR pipe at the rear of the engine. This short metal right angled pipe is attached at the inlet manifold end by two screws through an oval flange and to the engine block by a relatively large hexagonal pipe fitting, all of which appear impossible to access with spanners or sockets.
has anyone on the forum successfully attempted to remove the NC inlet manifold with the engine in situ? I’m currently scratching my head waiting for that Eureka moment. I’ve just read the post on here regarding EGR valve replacement. Do I need to start removing panels around the wipers to give me more access to the EGV pipe fixings? My inlet manifold is still hanging on the pipe with no apparent way to acces the fasteners.
I’ve done it, it’s do-able but as you’ve found out access is restricted. I used 1/4" drive socket, extension and ratchet. Removing the wiper assembly and the access panel below the windscreen will improve access slightly.
I went ahead and removed the service panel from below the wipers and scuttle. That has allowed me to finally reach the EGR pipe fitting (photo attached) with a 22mm open ended spanner. The inlet manifold or dynamic chamber as it’s called, is now loose, but something is still preventing me from lifting it upwards and away from the engine. I’ve studied photos of the inlet manifold after being removed (attached photo for ref only) and all it can be is either the knock sensor cable and plug below the manifold (lower right) or the short PCV valve connecting hose itself (lower left). If I can reach these and disconnect them I should be able to finally lift off the inlet manifold. It’s a lot of hassle just to replace a plastic £6 PCV valve, but I’m hoping it fixes my oil consumption problem. Whilst I’ve got access to the valve, I’m going to run some hoses to an oil catch can that I plan to install on the bulkhead behind the fuse box. At least that way I 'll have a visual indication of any oil escaping via the PCV line. I’d rather catch it, than burn it. TerryO.
Well, I finally managed to remove my inlet manifold from the engine and gain access to the PCV valve. I’ve replaced the PCV and have added a hose to take oil vapours to my oil catch can. The return from the catch can will attach back at the inlet manifold. I’ve added a 90 degree connection and hose to the mating port of the inlet manifold where the PCV normally feeds into.
Assembling the manifold back into place with the additional hose was not easy and took me several attempts before I could route the hose past everything else on that side of the engine.
It certainly pays to label everything as you remove it, which I did. I managed to get everything reconnected in order and the engine started with no problems. All I need to do now is mount the catch can on a suitable bracket and take the car for a run.
As I’ve used the clear reinforced PVC type hose normally supplied with catch cans, I’m going to add some wrap-around heat shield insulation to the hoses where they run close to the engine. Although there are lots of plastic components attached to the engine under the inlet manifold, I’m still not 100% sure how hot it will get where I’ve routed the hoses?
TerryO.
I assume you cleaned out the Oil Separator shown in your 2243 picture? This is supposed to be the built-in ‘catch can’, but can become clogged up if someone has used cheap oil in the engine or skipped filter changes.
No, I didn’t remove the cover that the PCV is attached to. I know this is supposed to act as an oil vapour separator. However, the car has a full Mazda service history and it was serviced by the same main dealer every year. In theory it should have regularly had new fully synthetic 5W-30 each year.
It’s all back together now, which is a relief. All I need now is a free weekend when I can take it out for a run!
TerryO.
I was going to ask if anyone knew how hot the short metal pipe becomes, situated between the ECR valve and the inlet manifold. My oil catch can hoses run quite close to this pipe and I understand that it feeds a small amount of exhaust gas back into the inlet air supply as part of the emissions system. Does anyone know if the pipe reaches exhaust type temperatures?
Well, it’s been 6 months since I installed the oil catch can and new PCV valve. The catch can didn’t really remove a great deal of oil vapour and my exhaust continued to smoke. Oil consumption continued to increase to the point where I was using 0.5 litre every 100 miles! Not good. The smell was not pleasant either, in the car or for those behind me.
Needless to say, I was a little concerned that it would fail the emissions test at the fast approaching MOT. Time for a replacement engine?
One month prior to the MOT I called the people at MX5Mania. Luckily for me they were just about to break a 2007 1.8i Icon. Low mileage at just 37k. I bought the complete engine and gearbox. Many thanks to Marlene and Rob for their excellent friendly service. I recommend MX5Mania for any used spares at a reasonable price. Whilst looking for a nearby garage to install the engine and gearbox I discovered that MX5 Heaven were right on my doorstep, just half an hours drive south of Yeovil in Charminster, near Dorchester.
Prior swapping out the engine and gearbox, MX5 Heaven gave the car an emissions test. The HC limit of 200 ppm was showing a best reading of 1200 ppm. A definite MOT failure.
Never the less, since having the replacement engine and gearbox fitted I’ve been using the MX5 every day and it hasn’t used a single drop of oil. Roll on the summer!
I wonder what caused the engine to fail in the first place? You say " full Mazda service history and it was serviced by the same main dealer every year. In theory it should have regularly had new fully synthetic 5W-30 each year " Do you think it ran low on oil and you didn’t notice? How many miles had it done?
Sorry, just interested.
D
What sort of mileage had the old engine done? The MZR engine isn’t weak. My guess is it was run without an air filter in the past, run in unusually brutally, or used for lots of very short trips.
